Unless otherwise indicated herein, the description in this section is not prior art to the claims in this application and is not admitted to be prior art by inclusion in this section.
A typical image forming apparatus, which forms images on sheets, includes a photoreceptor drum, developing device, and a transfer apparatus. After the developing device visualizes an electrostatic latent image formed on the circumferential surface of the photoreceptor drum as a toner image, the transfer apparatus transfers the toner image to a sheet. The transfer apparatus includes a transfer roller. The transfer roller is in abutting contact with the photoreceptor drum and rotatably driven. Applying a transfer bias to the transfer roller forms a transfer electric field in which toner moves from the photoreceptor drum to the transfer roller.
There is disclosed a certain technique that applies a cleaning bias to a transfer roller to remove toner attached to the transfer roller made of a rubber material. The technique stops applying the cleaning bias for a predetermined period after an image forming operation is terminated to solve a bleeding phenomenon, which is a phenomenon where remaining low molecular materials (impurities) on the transfer roller exude in the form of oil.